memorycopy

Memorycopy refers to the operation of copying a contiguous block of memory from a source address to a destination address without interpreting the data. It is a low-level primitive used to move raw bytes and is a common building block for higher-level operations such as string handling, buffering, and data serialization. In many programming environments the operation is exposed by a standard library function often named memcpy or Buffer.BlockCopy, depending on language and runtime.

Typical signature in C is void *memcpy(void *dest, const void *src, size_t n); it copies exactly n bytes from src to dest and returns dest. It does not guarantee safe behavior if the source and destination buffers overlap; in that case, the behavior is undefined for memcpy, whereas memmove is defined to handle overlaps by using an intermediate buffer or directional copy.

Performance is highly optimized; modern libraries use architecture-specific instructions and non-temporal stores to maximize bandwidth. The operation may be implemented with loops, vector instructions (SSE/AVX), or specialized memory copy engines in CPUs or accelerators. Alignment and cache friendliness influence throughput; copying large blocks is usually much faster when source and destination are aligned and cached efficiently.

Care is needed to ensure the specified memory regions do not overlap for memcpy; ensure the correct number of bytes is copied to avoid buffer overruns; in managed languages, memorycopy may bypass type safety and must be used with care to avoid exposing sensitive data or causing security issues. When overlap is possible, use a safe variant such as memmove or equivalent.

Memorycopy is a fundamental operation across systems, embedded, user-space libraries, and kernel code, forming the basis for memory management, I/O buffering, and inter-process communication.